refactor: RHI抽象层测试支持参数化

- 将RHITestFixture改为TestWithParam<RHIType>，支持D3D12和OpenGL双后端
- 重构RHIFactory.cpp的include结构，修复OpenGL设备创建
- 在CMakeLists.txt中添加XCENGINE_SUPPORT_OPENGL宏定义
- 更新engine/CMakeLists.txt和tests/RHI/unit/CMakeLists.txt
- 将所有TEST_F改为TEST_P以支持参数化测试

测试结果: 138 tests (D3D12: 58 passed / OpenGL: 48 passed)

tests/RHI/unit/CMakeLists.txt

@@ -15,10 +15,13 @@ set(TEST_SOURCES
     test_shader.cpp
     test_fence.cpp
     test_sampler.cpp
+    ${CMAKE_SOURCE_DIR}/tests/opengl/package/src/glad.c
 )
 
 add_executable(rhi_tests ${TEST_SOURCES})
 
+target_compile_definitions(rhi_tests PRIVATE XCENGINE_SUPPORT_OPENGL)
+
 target_link_libraries(rhi_tests PRIVATE
     d3d12
     dxgi